Pruning Basics

Why, When, & How to Prune

﻿Karlee﻿n S﻿h﻿afe﻿r﻿

Have you ever looked at the tangled mess of a tree, shrub, or vine and wondered where to begin? Differentfactors are key to successful pruning. These include: the reason for pruning, the type of plant, and the time of year. Pruning should not be done unnecessarily, as this can stress the plant. This article will highlight some pruning basics.Let’s start with some of the reasons to prune. The main reasons are:

Promote plant h﻿e﻿alth - Cutting out dead or broken branches that could invite disease or insects is a must. Storms can cause damage and create serious problems for plants. Branches that rub together should be removed. When removing large branches, care should be taken not to leave a stub. A stub leaves more than several inches sticking out from the tree.

﻿Maintain the plants intended purpose and direct growth - This includes maintaining a dense privacy hedge, tree, or overall garden form. Pruning should improve a plants appearance, but many times a plants natural form is best. The natural form only needs to be altered or confined to meet a specific need, like visibility out of a window. If you like your plantings sheared into tight geometrical forms, maintenance will be increased. Pruning should be used to keep the plant well proportioned, control its size, remove waterspouts, suckers, or unwanted branches.

Safety - Remove dead branches, hazardous trees, and weak branches to protect people and property. This may include branches that are too close to your house, sidewalks, and driveways, or branches that obscure vision for drivers. Keep plants near the entry to your home trimmed for security purposes. Contact utility companies or city public services for branches that interfere with street lights, traffic signals, or overhead wires.

Promote﻿ flowers﻿ and fruit - Pruning stimulates new growth.

Change the appearance of the plantings - Contour your shrubs or encourage their natural form with a light pruning to meet the aesthetic needs of your setting.

Many times someone has asked me, “Do I need to prune? If so, what shape is best?” For example, does a boxwood shrub need to be trimmed into a box shape? This is where the application of the planting (how it fits into our landscape,) comes into play. Is your home formal or informal? My home is rather informal, with a boxwood hedge lining steps to our front door. I keep these boxwoods minimally pruned just once a year, trimming them wider at the base and tapering to the top in a bit of a wedge. This keeps the hedge full and green. I have boxwoods in other areas of our yard that have a natural, vaguely round shape that I don’t trim at all. These boxwoods are not in a hedge and would look odd trimmed individually into little boxes. Hedges pruned into a uniform shape look very kempt, but a naturally shaped hedge can look orderly as well. Hedges serve as borders, natural fences, walls, edging, and screens. A well shaped hedge must be trained from the beginning, this allows sunlight to reach all of the leaves. It is best to trim a little at a time, gradually arriving at the desired shape. Spreading junipers should have the tip ends trimmed each year, which helps keep a compact growth habit. It’s better to select compact dwarf forms to fit your area than to do a lot of pruning.

﻿TreesTree pruning﻿ should start at planting. Trees should be trained to have a strong structure. The nursery may have already taken care of this step, but if you purchased one of those “bargain” trees you will want to remove any diseased, dead, or broken branches. Prune to shape, but don’t cut back the leader branch. Remove any cross branching and branches that grow toward the center of the tree. Also remove branches that are too closely spaced on the trunk and multiple leaders. Making pruning cuts correctly will encourage the rapid healing of wounds. Avoid tearing the bark when removing large branches. Trees such as oaks should only be pruned when the temperature is below freezing because of the chance of oak wilt disease. Conifers may be pruned any time of the year, but to minimize sap and resin flow from cut branches, prune during the dormant season. Trees that flower in the summer or fall should be pruned in the dormant season. Spring flowering trees should be pruned immediately after flowering. Many trees are susceptible to fire blight, a bacterial disease that can be spread by pruning. Check with your county extension agent for additional information.

Deciduous shrubsDeciduous shrubs that are newly planted do not usually need pruning for a year or two. Don’t forget them! The burning bush that was 3’ tall when planted can easily reach 6‐9’ in a handful of years. There comes a point when it’s very hard to reclaim the former shape. Thinning out the crown of shrubs will rejuvenate the plant, increase light, air circulation, and growth. I usually suggest trimming out 2‐3 stems per year for a gradual renewal, being careful to maintain the shrubs form. Thin out the oldest stems slightly above ground level before new growth starts.

Early BloomingShrubs that bloom early should be pruned immediately after they finish blooming. Some examples areazalea, chokeberry, cherry, forsythia, lilac, and magnolia. Spring blooming shrubs bloom on last seasonsgrowth, so should not be pruned until after flowering. Some shrubs that bloom after June usually form shoots that grow the same spring and should be pruned in the dormant season.

RosesRoses should be pruned back to the live wood in the spring. This may be mid‐May in Michigan. When removing faded or spent flowers, cut down to the first five‐leaflet leaf. Pruning should be done at 45 degree angles, about ½” above the bud. Additional pruning depends on the type of rose and further information can be found here: http://msucares.com/lawn/garden/flowers/perennial/roses/pruning-diagrams.pdf

HydrangeasHydrangea is a shrub that has different cultivars that bloom on old wood, new wood, and some on both. I suggest hydrangeas that bloom on new wood for our area. You will receive more blooms with them, as some cultivars that bloom only on old wood may suffer from late freezes. Be sure to ask when you purchase.

VinesVines many need trimming back and pruning for a clean, well kept appearance. Pruning methods for vines vary, not only for the different vines, but also for the cultivar. Clematis has Spring, Summer, and Fall times to prune, depending on the cultivar. Always check your information with MSU Extension or ask your local nursery.

GrassesEnd of March or April is the time totrim back ornamental grasses in Michigan. The grasses can be tied and a hedge trimmer used to cut off all at once. If trimming later in the season, newer growth will also be cut off.

PerennialsPruning is also beneficial for perennials. Pruning is done to shape, to control growth, and increase flowering. Pruning will extend the bloom time, regenerate the plant, and encourage a repeat bloom.

Start right by considering the ultimate size of shrubs and trees. It is an important step to a great landscape.